GUNS Magazine December 2010 - Page 16

• JACOB GOTTFREDSON • Swarovski’s new scopes feature an improved holdover system using the BRX Reticle. have put some ink to paper in the last several columns about budget-minded optics. I thought I would change directions for a while and look at optics on the other end of the spectrum. From $300 to just short of $3,000 is a huge leap. Are they worth it? I acquired two new Swarovski optics I have a particular interest in for our magazine: A new hunting scope and the newest evolution in their binocular series. I’ll get to them soon, but since I’ve been writing about the use of holdover bars, let’s explore one of Swarovski’s new reticle offerings; one I am particularly fond of first. plane variable scope. If the first focal plane is used, the spacing remains the same, regardless of the power. If you SUVARi rest your rifle mENA on bags with the reticle aimed at a 1-MOA grid, the first bar below the main horizontal crosshair GlASS WiTH ClASS I Swarovski’s TDS Reticle I will be the first to admit I have belabored the hashmark reticle concept in this column, and I promise this will be my second to last for a while. However, once thoroughly understood, hashmarks will increase productive hits tremendously. One of the first, if not the first, holdover bar reticle system, disregarding the military’s mil dot reticle, was introduced by Swarovski. It was called the TDS Tri-Factor Reticle after Col. Tom Smith who came up with the concept. It was so simple and yet so complicated it almost defied reasonable explanation, but it worked! Many variations of holdover bars have been introduced by other manufacturers, and some of them work off the same principle as Col. Smith’s. Some look-alikes do not. For example, some holdover bars use constant subtention spacing between the bars. However, several models of Swarovski, Burris, Zeiss and Leupold use progressive subtension. Let me explain. The simplest way to design holdover and ranging bars is to space the bars so they subtend some constant dimension at 100 yards. For example, the Nightforce NP-R2 reticle bars are spaced at a constant 2 MOA at the scope’s highest power. That spacing changes (increases) when the power is reduced on a second focal 16 theoriginaltDStri-Factorreticleusedby Swarovski(above),isnamedafterCol.tom Smith,whocameupwiththeconcept.the newBRX(below)increasesthenumberof holdoverbarsanddotsaswellasplaces verticalwindbarsatthehalfpoints.the progressivesubtensionpatternofthe holdoverbarsisalsoslightlydifferentthan theoriginal. will be on the second grid line, the next bar on the fourth grid line, the third on the sixth grid line, etc. that is, on a constant subtension spacing. Many of these holdover bars are also of a constant length and width. The other type of reticle holdover bars (that look the same as the Nightforce) are a bit more complicated in that the spacing of the bars is progressive. That is, the spacing is increased on some predesigned pattern. For example, the Swarovski BRX holdover bars are spaced at 1.8", 5.4", 9", 12.6", and 16.2" with a dot in between. The original TDS TriFactor reticle had similar spacing at approximately 2", 4.8", 7.5" and 10.5". Some Leupold, Zeiss, and Burris models follow similar patterns. To understand the logic behind the progressive spacing, you have to think in terms of the ballistic trajectories of modern cartridges and the bullets used. The genius of Col. Smith was in recognizing these trajectories could be emulated by the use of drop factors and was determined by noting the bullet’s drop. The 7mm Remington Magnum might be a factor of six, while the .308 might be a factor of eight, or the drop at 300 yards when the rifle was sighted in at 200 yards. The subtension spacing he came up with after a good deal of ballistic research and experimentation could be used acceptably to emulate the ballistic path of almost any modern cartridge. Enter Swarovski’s New BRX Reticle Working on this theme, Tom Hogan of Swarovski, refined and expanded the original TDS concept. The design is simple and elegant. Using modern ballistic software, Mr. Hogan revised the spacing and the length of the bars. He also converted all the dimensions from inches to metric and mils for those so inclined. The length of the bars allows the shooter to use them as wind bars as well. Each bar is subdivided by a WWW.GUNSMAGAZINE.COM • DECEMBER 2010